Geneva — In a dramatic turnaround, the Biden administration thanked the World Health Organization Thursday for leading the global pandemic response and vowed to remain a member state. “Under trying circumstances, this organization has rallied the scientific and research and development community to accelerate vaccines, therapies and diagnostics,” Dr. Anthony Fauci, who’s been named President Joe Biden‘s chief medical adviser, told a meeting of the WHO’s executive board.

The WHO, he said, had “relentlessly worked with nations in their fight against COVID-19.”

His comments marked a clear departure from the harsh criticism dealt to the WHO by former President Trump, who’d started withdrawing the U.S. from the organization.

But on his first day in office Wednesday, Mr. Biden reversed that decision.

In a letter sent to United Nations Secretary General Antonio Guterres, Mr. Biden announced he was retracting Mr. Trump’s July 6 notification that the United States intended to withdraw from the UN health agency in 12 months.

“The United States intends to remain a member of the World Health Organization,” Mr. Biden wrote.

WHO chief Tedros Adhanom Ghebreyesus hailed the about-face.

“WHO is a family of nations and we are all glad that the United States is staying in the family,” he told the executive board meeting.

In his address to the WHO on Thursday, via videolink, Fauci stressed that Washington — long the agency’s top donor — was committed to resuming its share of WHO funding. “The United States … intends to fulfil its financial obligations to the organization,” he said.

He also said Washington planned to “work constructively with partners to strengthen and importantly reform the WHO.”

Fauci stressed that the United States was aware of the towering task ahead in reining in the pandemic, which in just over a year has claimed more than two million lives, infected close to 100 million people and eviscerated the global economy.

“The United States stands ready to work in partnership and solidarity to support the international Covid-19 response,” he said.

Mr. Biden, said Fauci, was also preparing to issue a directive declaring U.S. intent to join the WHO co-led Covax facility, a globally-pooled Covid-19 vaccine procurement and distribution effort aimed at equitable vaccine access.

Fauci also mentioned an international mission finally underway in China to help investigate the origins of Covid-19.

Both the WHO and China have met with criticism that the mission is taking place more than a year after the first cases of the virus surfaced in Wuhan.

“We are committed to transparency, including those events surrounding the early days of the pandemic,” Fauci said.

“It is imperative that we learn and build upon important lessons about how future pandemic events can be averted,” he said, stressing that “the international investigation should be robust and clear, and we look forward to evaluating it.”